Symmetrical animals have paired body parts that are arranged on either side of a plane passing through the central axis. When any plane passing through the central axis of the body divides an organism into two identical parts, it is called radial symmetry. Such radially symmetrical animals have a top and bottom side but no dorsal (back) and ventral (abdomen) side, no right and left side. They have a body plan in which the body parts are organized in a circle around an axis. It is the principal symmetry in diploblastic animals. Cnidarians such as sea anemone and corals are radially symmetrical. However, triploblastic animals like echinoderms eg. Starfish have five planes of symmetry and show Pentamerous radial symmetry.
